Due to its excellent properties, poly(ethylene terephthalate) (PET) is one of the most produced and consumed polymers. Among plastics, it represents the main contributor to environmental pollution. ...Following the circular economy model, the chemical upcycling of PET reduces the amount of waste generated and transforms it into high-value products. The depolymerization of poly(ethylene terephthalate) into oligomers or monomers leads to forming a library of reactive molecules involved in different polymerization processes to obtain compounds with improved properties. Herein, several β-hydroxy amines were synthesized and used for the chemical recycling of water bottle waste by an environmental benefit aminolysis process to get very useful new terephthalamide diol monomers. The recycled diol monomers were subsequently exploited to synthesize poly(urethane acrylates) (PUAs) UV-curable coatings, and their chemical, thermal and mechanical characterizations were performed. The results show the great potential of the developed synthesis protocols to obtain PUAs with final properties that can be modulated to meet the requirements of different applications.
Poly(urethane-acrylates) (PUAs) are UV-curable resins used for biomedical applications, coatings, adhesives, and many others. Their syntheses usually involve the use of aromatic diisocyanates and ...polyols coming from fossil-based resources, in the presence of tin-based catalysts, which present a very well-known toxicity. In the last years the increase of environmental and economic issues related to the depletion of limited sources, the increase of greenhouse gas emissions, the release of toxic degradation compounds and the catalyst contamination has shifted the attention toward more sustainable solutions. In this study a low-impact, sustainable and efficient procedure for the synthesis of bio-based PUA promoted by solid supported CeCl3·7H2O–NaI/SiO2 was developed. This catalytic system provides the target compounds with good monomer conversion and molecular weights and allow the synthesis under heterogeneous conditions as main advantage, with the final recovery of the catalyst. We also confirmed its rapid separation, stability, and efficient recycling of the catalyst, obtaining comparable results over a seven reactions cycles. The goodness of the polymerization process under heterogeneous condition was confirmed by chemical and thermal characterizations.
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•Sustainable catalytic reactions play a key role in polymer synthesis, due to the continous demand for new valuable polymeric metrices and this work has been developed with this purpose:•PUAs synthesis avoiding the use of Tin based catalysts which have a very well-known toxicity.•An efficient synthetic methodology able to exploit the catalytic activity of non-toxic Cerium(III) based systems.•CeCl3·7H2O–NaI/SiO2 for PUAs synthesis that can be filtered and reused for sevent times; a clear advantage from an environmental and economic point of view. .•Novel bio-based PUA from PLA and l-Lysine diisocyanate, with comparable chemical and thermal properties.
The ciliate
produces the metabolite climacostol that displays antimicrobial activity and cytotoxicity on human and rodent tumor cells. Given its potential as a backbone in pharmacological studies, we ...used the fruit fly
to evaluate how the xenobiotic climacostol affects biological systems in vivo at the organismal level. Food administration with climacostol demonstrated its harmful role during larvae developmental stages but not pupation. The midgut of eclosed larvae showed apoptosis and increased generation of reactive oxygen species (ROS), thus demonstrating gastrointestinal toxicity. Climacostol did not affect enteroendocrine cell proliferation, suggesting moderate damage that does not initiate the repairing program. The fact that climacostol increased brain ROS and inhibited the proliferation of neural cells revealed a systemic (neurotoxic) role of this harmful substance. In this line, we found lower expression of relevant antioxidant enzymes in the larvae and impaired mitochondrial activity. Adult offsprings presented no major alterations in survival and mobility, as well the absence of abnormal phenotypes. However, mitochondrial activity and oviposition behavior was somewhat affected, indicating the chronic toxicity of climacostol, which continues moderately until adult stages. These results revealed for the first time the detrimental role of ingested climacostol in a non-target multicellular organism.
The review highlights the main results of two decades of research on climacostol (5-(2
)-non-2-en-1-ylbenzene-1,3-diol), the resorcinolic lipid produced and used by the ciliated protozoan
for ...chemical defense against a wide range of predators, and to assist its carnivorous feeding. After the first studies on the physiological function of climacostol, the compound and some analogues were chemically synthesized, thus allowing us to explore both its effect on different prokaryotic and eukaryotic biological systems, and the role of its relevant structural traits. In particular, the results obtained in the last 10 years indicate climacostol is an effective antimicrobial and anticancer agent, bringing new clues to the attempt to design and synthesize additional novel analogues that can increase or optimize its pharmacological properties.
Climacostol (5-(2
)-non-2-en-1-ylbenzene-1,3-diol) is a resorcinol produced by the protozoan
for defence against predators. It exerts a potent antimicrobial activity against bacterial and fungal ...pathogens, inhibits the growth of several human and rodent tumour cells, and is now available by chemical synthesis. In this study, we chemically synthesized two novel analogues of climacostol, namely, 2-methyl-5 (2
)-non-2-en-1-ylbenzene-1,3-diol (AN1) and 5-(2
)-non-2-en-1-ylbenzene-1,2,3-triol (AN2), with the aim to increase the activity of the native toxin, evaluating their effects on prokaryotic and free-living protists and on mammalian tumour cells. The results demonstrated that the analogue bearing a methyl group (AN1) in the aromatic ring exhibited appreciably higher toxicity against pathogen microbes and protists than climacostol. On the other hand, the analogue bearing an additional hydroxyl group (AN2) in the aromatic ring revealed its ability to induce programmed cell death in protistan cells. Overall, the data collected demonstrate that the introduction of a methyl or a hydroxyl moiety to the aromatic ring of climacostol can effectively modulate its potency and its mechanism of action.
We synthesized and characterized MOMO as a new small molecule analog of the cytotoxic natural product climacostol efficiently activated in mild extracellular acidosis. The synthesis of MOMO had a key ...step in the Wittig olefination for the construction of the carbon-carbon double bond in the alkenyl moiety of climacostol. The possibility of obtaining the target (
)-alkenyl MOMO derivative in very good yield and without presence of the less active (
)-diastereomer was favored from the methoxymethyl ether (MOM)-protecting group of hydroxyl functions in aromatic ring of climacostol aldehyde intermediate. Of interest, the easy removal of MOM-protecting group in a weakly acidic environment allowed us to obtain a great quantity of climacostol in biologically active (Z)-configuration. Results obtained in free-living ciliates that share the same micro-environment of the climacostol natural producer
demonstrated that MOMO is well-tolerated in a physiological environment, while its cytotoxicity is rapidly and efficiently triggered at pH 6.3. In addition, the cytostatic vs. cytotoxic effects of acidified-MOMO can be modulated in a dose-dependent manner. In mouse melanoma cells, MOMO displayed a marked pH-sensitivity since its cytotoxic and apoptotic effects become evident only in mild extracellular acidosis. Data also suggested MOMO being preferentially activated in the unique extra-acidic microenvironment that characterizes tumoural cells. Finally, the use of the model organism
fed with an acidic diet supported the efficient activity and oral delivery of MOMO molecule
. MOMO affected oviposition of mating adults and larvae eclosion. Reduced survival of flies was due to lethality during the larval stages while emerging larvae retained their ability to develop into adults. Interestingly, the gut of eclosed larvae exhibited an extended damage (cell death by apoptosis) and the brain tissue was also affected (reduced mitosis), demonstrating that orally activated MOMO efficiently targets different tissues of the developing fly. These results provided a proof-of-concept study on the pH-dependence of MOMO effects. In this respect, MOM-protection emerges as a potential prodrug strategy which deserves to be further investigated for the generation of efficient pH-sensitive small organic molecules as pharmacologically active cytotoxic compounds.
The occurrence of unsaturated systems in natural products combined with the mildness and the wide range of applicability of CeCl(3) promoted methodologies suggest several potential future synthetic ...applications within the field of total synthesis of biologically active molecules. On this concept, the use of CeCl(3).7H(2)O-NaI system as an efficient heterogeneous promoter has been highlighted in the iodofunctionalization of carbon-carbon triple bonds. The study has shown that this method would be particularly interesting for the stereoselective formation of trisubstituted (Z)- or (E)-iodoalkenes by simply changing the nature of the solvent. The methodology has been successfully applied to the synthesis of (R)-1-4,4-bis-(3-methyl-2-thienyl)-3-butenyl-3-piperidinecarboxylic acid , named (R)-Tiagabine, which is a potent and selective gamma-aminobutyric acid (GABA) uptake inhibitor with proven anticonvulsant efficacy in humans.
A big challenge for the civilization in energy saving/waste management can be “the regeneration of monomers from the waste plastics followed by their re-polymerization” using an ideal recycling ...method. Herein, we investigate the thermal depolymerization of poly(methyl methacrylate) (PMMA) using thermogravimetric analysis coupled with mass spectrometry (TGA-MS). In this process, the polymer chains were decomposed to methyl methacrylate (MMA) in high yield and the degradation species were thoroughly characterized. The obtained MMA contained traces of byproducts. Firstly, the byproducts were found to be nonpolymerizable, secondly, their presence interrupt the polymerization reaction, and thirdly, they reduce the quality of re-polymerized PMMA (r-PMMA). This study reclaims that besides the main byproduct (methyl isobutyrate), traces of methyl pyruvate and 2,3-butanedione were also formed during the thermal depolymerization of PMMA. The formed 2,3-butanedione was found to be responsible for the unpleasant smell in the recovered MMA that also found itself in the r-PMMA. Further, the generated byproducts were eliminated from the r-PMMA by a dissolution/re-precipitation method. The structural characterizations of the recycled and purified PMMA were carried out by Fourier-transform-infrared spectroscopy (FT-IR), Hydrogen-1 (1H)- and Carbon-13 (13C)-nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC) and gel permeation chromatography (GPC). The chemical properties of the r-PMMA and purified PMMA proved to be similar to that of the virgin commercial PMMA. This study can provide an effective and practical prototype for the recycling of waste PMMA scraps and thus reduction in pollution caused by the landfilling of waste PMMA scraps.
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•Depolymerization of waste PMMA for MMA recycling was investigated.•PMMA could efficiently be depolymerize by pyrolysis at high temperature.•From the recovered MMA, further PMMA products could efficiently be produced.•Formed byproducts in the pyrolysis were eliminated by dissolution/re-precipitation.•Chemical properties of reproduced PMMA found to be similar to that of virgin PMMA.
Readily preparable morpholine amides hitch in good yields with organocerium reagents to produce ketones. Even in the presence of substrates and reagents with high steric hindrance, the organometallic ...compounds prepared from dry cerium(III) chloride and organomagnesium or organolithium compounds at -78 degrees C add cleanly to morpholine amides. The low cost of starting materials makes this new scheme of synthesis very interesting for the preparation of biologically important pheromones.
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